Back up my Debian 4 etc because of ISP 2.2.21 question

1. I have installed Debian 4 etch with ISPConfig 2.2.18 and my questions is can I update it to 2.2.21 without previous versions 2.2.19, 2.2.20 ?? I mean is this correct
2. I have more than 200 email accounts on my server, so first I think to make a back up of my server. So I think to use Partimage (here I find a guide: http://www.debianadmin.com/backup-and-restore-linux-partitions-using-partimage.html)
For example when I type: #fdisk -l , this is the result -

3 And after that I think to upgrade to 2.2.21 , I know that it makes it owns back up but I want to do all this because some of my friends tell me that they have some problem while updating ISPConfig and now they don't do the updates..

So please tell is all this is right and if you have any suggestions about other back up software please tell me

Thank you falko. I visit this page and see many different ways to create backup. I like SystemImage , Amanda, but they and most of the other softwares are using backup-host and backup-client , or they are transfering images to an FTP server. In my case I have only one server - it's alone and I can't connect second computer to network , so I search how to make a backup locally and after that transfer it to an external HDD. That's why I was thinking to use PartImage
because it doesn't need other pcs. Do you think PartImage is not good ? And what software you prefer to use for backups falko ?

Zesterdaz I made a backup with Ghost4Linux - all was good except one thing - it was very slowly , and during the back up server was not working (and it's an email server). Today I will try PartImage - because it can be used remotely - you don't need to be infront of the server